The invention relates to a fuel supply system for an internal combustion engine having a fuel injection pump for conveying a controlled amount of fuel to be injected into the engine. These systems have a fuel feed pump for feeding fuel under pressure to the intake chamber of the fuel injection pump, and in such an arrangement, it is conventional to control the temperature of the fuel fed to this injection pump via the fuel feed pump disposed externally of the injection pump. For this purpose, the outside air temperature, or the exhaust air temperature of the heat exchanger for the cooling cycle of the internal combustion engine, is detected with the aid of a temperature sensor, and the distribution of the fuel fed to the injection pump, by way of a heater-type heat exchanger and a bypass conduit connected thereto, is controlled according to this temperature.
This arrangement solves the problem of increasing the fuel temperature with an increase in the outside temperature, thus reducing the amount of injected fuel effective for the combustion process, but entails the disadvantage, in that this control procedure is affected adversely if the amount of injected fuel is to be regulated accurately by volumetric metering in order to attain a maximum of efficiency without exceeding the limits of the maximally permissible content of deleterious substances in the exhaust gas. Even with this arrangement which, by the way, is very expensive, the effective amount of fuel fed in metered amounts varies greatly with fluctuating outside temperatures and an ensuing fluctuating density of the fuel which gradually adapts to this temperature. Consequently, large tolerances must be provided for the regulation of metered fuel fed to the system, or effective compensating units must be additionally included.